Edible, wholly or partially non-digestible low calorie fat materials and methods for the preparation thereof are known. Much has been written about the adverse health problems of high fat diets, thus indicating clearly an interest in and a need for a fat substitute that is either entirely non-digestible, or has a reduced caloric value. The recent interest in non-caloric food substitutes has resulted in several classes of compounds being proposed. One suggested class has been esterified propoxylated glycerins. However, because the recommended methods of preparation either required toxic catalysts which cannot be completely removed or result in a product with unacceptable acidity, new process methods are needed. The instant invention overcomes these problems.
European Patent No. 254,547 discloses that esterified propoxylated glycerins can be used as non-caloric food substitutes. References cited therein provide a good review of the field relating to fat substitutes, methods for their preparation and problems associated therewith. Two methods of preparation are described in EP 254,547 none of which can be used to prepare a food grade product. The preferred method is to react fatty acids with a propoxylated glycerin using p-toluenesulfonic acid as catalyst allowing catalyst residues at unacceptable levels even after purification. An alternative method, which is exemplified in the examples, reacts the propoxylated glycerin with a fatty acid chloride in the presence of a tertiary amine such as pyridine. Not only would such methods be technically impractical for commercialization but would require column chromatography for any purification.
U.S. Pat. No. 3,337,595 describes a method for preparing fatty esters of propoxylated glycerins where the propoxylated glycerin has a molecular weight above 600. These esters are disclosed as being useful for controlling, suppressing and/or preventing foaming of aqueous systems having foaming tendencies in industrial processes. The process is not suitable for preparing food grade products. The acid values (maximum of 25 KOH/g) are much too high for an edible oil. Only stoichiometric quantities of reactants are employed resulting in a method too slow for a practical commercial process.
U.S. Pat. Nos. 4,517,360 and 4,518,772 describe processes for preparing sucrose polyesters by the catalytic transesterification of sucrose with fatty acid methyl esters in a solventless system wherein part of the fatty acid esters is converted to a fatty acid soap by hydrolysis with an alkali metal hydroxide such as KOH. This in turn required complicated purification where water was added to the reaction product and the mixture certrifuged to remove the soaps and catalyst. The final organic product was purified by vacuum steam stripping and decolorization.